Hmmm...
I'm just thinking off the top of my head...
Have you tried submitting your Tech Support request here?:
http://www.musicmatch.com/form/support/customer/
(this seems to be a back door to the help desk and you can enter your registration key - I think)
Perhaps you might try re-installing your registered version 7.2 and submit your Tech Support request regarding 9.0 - maybe then you will get the Tech Support Desks attention.
If you bought "All Future Upgrades" obviously you should not pay another cent. But - if things get really bad, maybe you could pay the 20 bucks, register and then ask for a refund???
Almost off-topic. I think MM is great, but it does have some annoying startup defaults which I just cannot figure out how to change - its starts playing any CD in your drive without asking and it automatically looks for an internet connection.
One more idea - maybe you can try killing any internet connections before launching 9.0 for the first time. It will probably take a minute or two to launch, but eventually it will give up looking for connection. Try plugging in your registration key immediately.
Yet another idea - could it be a proxy issue? There are proxy settings on the Options/Settings/Connectivity menu. In fact, there is an option to disable automatic Internet Connection Check! (Hey, I'm learning things here!) Do you have any pop-up blockers, firewalls active - maybe try disabling temporarily until you can get through the registration process.
I still have not found a decent user forum for MM - weird...